[DOC] Explain how to take over an abandoned feedstock

I’m actually not sure if this is already documented but I at least cannot find it anywhere.

It would be good to have the process of taking over an abandoned feedstock documented somewhere.

The workflow for this is generally:

1. Create a PR and add your GitHub username to the meta.yaml (The current maintainer should not be removed, only if they later request so)
2. Rerender with smithy
3. Ask core by pinging them or in gitter to merge the PR
4. Fix any pending PRs and update the feedstock, if necessary.

Prerequisites:

A feedstock is generally considered abandoned if the maintainer is not on GitHub anymore or if multiple bot PRs are open. An exact definition can be found here: https://github.com/conda-forge/cfep/pull/15 although that is not yet accepted. Therefore that part is currently on a case-by-case basis and decided by core.

[PrernaSingh587]

@PrernaSingh587 thank you for working on this issue 😃. But I was working on it and was about to make a PR. Next time while working on some issue please make sure to check whether someone else is already working on it 😃

Actually this was stagnant since 6 days with no activity. Also no one was assigned. So thought to raise a PR. 😃

[BastianZim]

I would again defer that @viniciusdc 😄